Teeemal circuit changee and peotective



(No Model.)

H. A. RHODES. THERMAL GIRGUIT CHANGER AND PROTECTIVE APPLIANCE. No. 484,822.. Patented 001;. 25, 1892'.

(figd 519 4. lam I 2w 7' E? UNITED STATES PATENT OFFICEQ HARRY A. RHODES, OF DENVER, COLORADO.

THERMAL CIRCUIT-CHANGER AND PROTECTIVE APPLIANCE.

SPECIFICATION forming part of Letters Patent No. $84,822, dated October 25, 1892. v v Application filed March 11, 1892 Serial No. 424,539. (No model.)

To aZZ whom it may concern.-

Be it known that I, HARRY A. RHODES, residing at Denver, in the county of Arapahoe and State of Colorado, have invented certain Improvements in Thermal Circuit-Changers and Protective Appliances, of which the following is a specification.

My invention relates to the protection of electrical apparatus and stations from the destructive effects of unduly-strong electrical currents which may at any time reach and traverse the circuits with which such electrical apparatus is associated by reason of an undesigned contact of the said circuits with others which properlyconduct the said destructive currents for the supply of electriclighting or power-translating devices or other analogous systems requiring for their operation currents of great strength and volume.

Its object is to provide an efficient automatic thermal circuit-changer adapted to respond to the passage of a sufficiently-strong current through an electric circuit with which it is connected through the intermediation of the heat developed by the passage of such current and thereupon to close, open, or otherwise change the condition of a second or aux.- iliary circuit or to change the condition of the actuating-circuit itself, which circuitchanger, moreover, shall be capable of automatically reversing its operation and restoring the original condition of the circuit or circuits upon the cessation or disappearance of the current to which its initial action was attributable.

A further object of my invention is to provide a satisfactory and trustworthy protective appliance for electric, and particularly for telephonic, apparatus and circuits which shall be prompt and certain in its operation, sure in result, and automatic both in coming into and going out of action, and which, furthermore, shall be capable of exercising its protective functions a great number of times without disarranging its own mechanism and without requiring attention or adjustment. It is well known that stray currents of the greatest strength are not the most dangerous and that such as are merely of strength sufiicient to gradually heat the magnet-wires of telegraphic and telephonic apparatus or ofdisastrous results. Heavy currents-say hav-- ing a strength of'several ampres-can be guarded against by properly-proportioned fuses. Experienceand trialhasdemonstrated that sneak-currents are best guarded against by either thermal or electro-magnet appliances; but if applied to telephonic circuits electro-magnets interpose a very considerable apparent resistance, consisting in part of true resistance and in part of the counter electromotive force of self-induction, and for this reason, and also for the reason that thermal protectors properly constructed are extremely responsive, I prefer them.

My invention consists in combining a substance having a high coefficient of expansion under varying temperature, and which is elasticsuch as mercury or alcoho'linclosed in a vessel or chamber ofadjustable capacity having a side or wall which is elastic and highly expansible, but of very considerable rigidity or stiffness whether in its expanded or normal condition, with an attenuated and concentrated section of an electric circuit embedded in or closely approximated to the said inclosed substance, so as readily to subject the same to changes of temperature as the strength of the current flowing in the circuit varies, and with a circuit-changer adapted to be mechanically acted upon by the said elastic side or wall of said chamber and to move in one direction when the heat of the attenuated section of conductor rises in correspondence with an increase of current strength in the circuit and in the other direction as such current and its accompanying heat diminishes.

It consists, also, in a specific construction of an appliance embodying the above characteristics and comprising a non-conducting chamber, a flexible and expansible diaphragm or membrane closing the same, mercury or alcohol inclosed therein, a heat-concentrab ing section of insulated conductor of small volume embedded in or in close juxtaposition to the said expansible inclosed body and adapted to be connected in and with an electric circuit, and a switch or circuit-changer which may form a part of the circuit within which is included the said insulated conductor, form part of an independent circuit, or which may be simply a mechanical switchoperating or mechanism releasing-lever.

It consists, also, in certain other combinations of electric apparatus and details of construction more fully described in the several clauses of claims which are appended to this specification.

In the drawings, Figure 1 is a side elevation of my appliance shown as being associated with an electric circuit for the protection of a call-receiving apparatus. Fig. 2 is a top view thereof. Fig. 3 is a horizontal section on the line 0c 00 of Fig. 1. Fig. 4 is a detached view of one form of the expansible-conductor-containing chamber. Fig. 5 is a sectional elevation of the same associated with the approximate parts of a switch adapted to be actuated by the expansible inclosed medium. Fig. 6 is also a sectional elevation as it appears afterhaving come into operation. Fig.

4 shows the heat-concentrating section of conductor in its actual size; Fig. 7, a portion of an associated lightning-arrester or disruptive-discharge-protective device; and Figs. 8 and 9 show my appliance associated with two circuits in such a way that an undue rise of current strength in one is enabled to produce adefinite change in the condition of the other.

The drawings represent, substantially, the actual size of a complete appliance which has been successfully employed in practice.

In Figs. 1 and 2, F is a base-board of wood or like material, and F is an upright wall or partition of the same material secured thereto.

The several elements of the appliance B may be all mounted on the upright partition F but I prefer to secure the parts toa background plate of hard rubber or similar material and to connect the electric parts thereof with the circuit by providing suitable contact-surfaces and by arranging that these shall register with contact-spring c, which leads to a ground-Wire w; 0 which virtually is the line-terminal leading into the appliance, and 0 which is the continuation lineterminal leading out to the'instrument or apparatus to be protected and to the groundwire or return-conductor.

Before referring in detail to the operative parts of my invention as combined in a protective appliance I will describe them first without regard to any such combination and will show their adaptation to the operation of circuit-changers generally.

Referring to Figs. 4, 4, 5, and 6, an inclosing chamber 72 is made of vulcanite or hard rubber, vulcanized fiber, or some similar suitable material which is a non-conductor of heat and electricity and is provided with a closelyfitting plug a of like material, which enters the said chamber to a greater or lesser extent, and thus regulates the internal size and capacity of such chamber.

Fig. 4 well represents in perspective the size and shape of an inclosed chamber which has been made and satisfactorily used in connection with a Working appliance. There is no need, however, of making it with square and rectilinear sides, except that when so made itis easily and conveniently secured, as in Figs. 1 and 3, where it is shown as being fixed in position against the abutting bar "1' by means of the screw 3, which passes through a threaded hole in the abutting plate or post 7. The chamber bored in the non-conduct ing block 91 may be bored entirely through it; but I prefer to form the same leaving a thin wall Z of the substance of the block at the end, which is then perforated or pierced by a smaller hole 0, through which, the closingplug n being in place, a medium which elastically expands when heated is, if it be a fluid, introduced. Either mercury or alcohol will answer; but I have found mercury to be peculiarly efficient, and a single drop or globule answers well. Before putting in the plug a a device capable of speedily becoming heated upon the passage of an electric current which is even but slightly stronger than that for which the circuit is designed and which for the said passage of the current must be a conductor and a portion of the main circuit is placed within the chamber, and its terminals are allowed egress down the sides of the plug. A well-known contrivance for this purpose and one which I have found useful is a small coil of fine insulated wire of somematerial havingahigh specificresistauce. Iron, German silver, or platinum will answer. I have found that a coil of No. 36 German-sit ver wiresutficientlylong to have a resistance of about twenty-five ohms and insulated with two coverings of silk, asbestus, or other insulating material which can withstand a considerable rise in temperature. The said coil of fine wire 70 when in place lies within the chamber between its end and the end of the inclosing plug, resting on the latter, and is embedded in the mercury or alcohol 6, which surrounds it and permeates its interstices. The upper end of the block a is closed by an expansible and elastic or flexible diaphragm 19, made of thin sheet-rubber or like material, which is secured thereto by bicycle-tire or other adhesive cement or, if desired, by a perforated screw-cap or gland. This, while securely sealing the mercury, expands outwardly as the mercury expands, as shown in Fig. 6, and furnishes a direct and rigid drumhead or mechanical contact capable of raising a lever d, a weight, or other device which it is desired to actuate. At the same time it antomatically regulates the capacityof the chamber, keeping the pressure of the mercury upon the heating-coil uniform and causing the same (regardless of any position in which the device may be placed) to return when cool to its usual and normal position in the chamber.

Recapitulating, it now appears thatn is the hard-rubber case or chamber; 71 its adjustable closing-plug; 7c, the heatconcentrating coil, having ends 2 and 3 for attachment with the circuit; e, a drop of mercury or alcohol placed in the chamber upon and around the coil, and p the elastic diaphragm closing the chamber on the side opposite to the plug n The coil of fine insulated Wire 70 can by its ends 2 and 3 beincluded in any desired-main circuit L. In Fig. 5 it is assumed that such current as may be flowing in said circuit is normal, and hence does not develop sufficient heat in the coil 70 to expand the mercury and bulge out the expansible diaphragm; but in Fig. 6 the contrary-is the case and the expan sible and elastic diaphragm p is shown as having been bulged outwardly by the enlargement of the chamber withinnmade necessary by the expansion of the mercury and the increased pressure brought to bear on said diaphragm. Alightcircuit-changingspringdis fixed at one end 61 and movable at the other end, where it lies close to the surface of the diaphragm p and free to be moved outwardly by the outward expansion thereof. It may be provided with a convex contact-piece d as shown in Figs. 5 and 6,where said contact-piece in Fig.5 is out of contact with afixed contactbar W and in Fig. 6 has been moved by the expansion of the diaphragm 19 into contact with said bar. It may, moreover, be aportion of an electrical circuit or may be simply a portion of a mechanism.

In Fig.8 the expansion of the diaphragm p and the consequent elevation of the spring d tends to close a normally-open alarm-circuit, a movable contact-point g, carried by said spring, being adapted thereby to be pressed against a fixed contact and limit-stop 9 The circuit of the battery S is thus closed through wire 13, fixed contact 9 movable contact g,

spring d, wire 12, and bell M and an alarm will be given.

' In Fig. 9 the same expansion and elevation of the spring d tends to open a normallyclosed circuit, the said spring lifting the movable contact g from the fixed contact 9 and, the armature of the annunciator N being released, its shutter will fall, giving a visual signal.

In Figs. 1, 2, 3, and 7, which refer more particularly to the use of my invention in a protective appliance for telephonic apparatus, it is associated, usually, with a lightning-arres'ter or a discharger consisting of two closelyapproximated plates at and Z7, preferably of carbon, connected, respectively, with the two sides or conductors L and G of the circuit. These may conveniently be held in place by making them in the form of angle-plates f, Fig. 3, and by placing metal plates m and m within the angles and securing the whole to the rubber base by screws. The said metal plates also serve to makegood contacts with heating-coil k.

the terminal springs c and 0 One of the wires 2 of the heat-concentrating 'coil 7c is attached by one of the screws s to the metal plate m and theother wire 3 is united to a screw yin the metal post 1". wire L of the main circuit, after passinga fuse H of sufficient capacitysay five amperes connects with spring 0 This presses against metal plate m and from thence the circuit continues by wire 2, coil is within the chamber 92, wire 3, metal post 7', spring 0 wire 4, annunciator A, and wire 5 to return-conductor or earth wireG. The movable contactspring dis fixed at one end 11 to the plate m and its free end, furnished witha contactpiece 61 lies upon or immediately over the expansible diaphragm 19 of the mercury-inclosing chamber. This spring is therefore anormally-discontinuous branch of the main circuit, connected therewith at a point outside of the annunciator and also outside of the course be substituted for said spring. A metal plate W is connected metallically at one end with the carbon-holding plate m and extends along the top of the entire appliance immediately over but not in contact with the spring at, The spring 0, which presses against the side of the plate m, is connected by wire 10 with the return-conductor orearth wire G. Thus the plate W is literally an earth branch. WVhenever the spring at by its contact-piece d is forced into contact with the plate W, the annunciator A and protective coil are evidently short-circuited and the circuit is put to earth.

In operation as long as the current is normal the spring contact-piece 1 will not touch the plateW; but the moment that an undulystrong current passes through the circuit the heat of said circuit will concentrate in the fine-Wire coil 70 and will pass therefrom to the mercury. This will expand and, if the heat becomes intense, will volatilize, although the appliance is so prompt and sensitive that the latter rarely can happen. sheet-rubber diaphragm p is .expanded and bulges outwardly, assuming a hemispherical form. In its expansion it necessarily pushes the spring 01 before it, and thus causes the piece (1 to make contact with the plate W, switching the dangerous current from the annunciator and protective coil to earth and concentrating its entire energy upon the fuse H, which, if the current be of sufficient strength, will be destroyed and will open'the circuit.

It has been found in practice that currents of less than half an ampere readily and promptly cause my appliance to operate, and,

furthermore, that, having operated, it is not destroyed, but is capable by reason of the prompt contraction of the mercury or other inclosed agent of automatically restoring the normal condition of the apparatus upon the cessation of the fault, provided that the ultimate current is not so strong as to blow out the fuse and is also capable of effecting its The incoming A light pivoted lever may of IIO In either case the protective function a large number of times without damaging its own mechanism and without attention.

I claim- 1. In a thermal protective appliance, a main conductor of an electric circuit, an earth or return conductor of the said electric circuit, a hollow cylinder or chamber of hard rubber or like material closed at one end and made of any desired normal capacity by a plug of the same materiahan attenuated and concentrated section of the main conductor of said electric circuit-such as a coil of fine insulated wire of relatively-high resistance-inclosed within said chamber, a globule or drop of mercury placed, also, within said chamber upon and around said coiled conductor, an elastic, flexible, and expansible diaphragm closing the remaining end of said chamber and suitably secured thereto, a conducting plate extending from the return-conductor to a point opposite to said expansible diaphragm, and a normally-discontinuous branch of the main conductor in the form of a light spring carrying a oontactpoint extending between the said plate and the said diaphragm and adapted upon the expansion of the latter to be moved into contact with the former, and

thereby to unite the main and return cond uctors directly and short-circuitthe inclosed coil of line wire, substantially as described.

2. In a thermal protective appliance, a vulcanite inclosing cell closed at one end by a tightly-fitting plug whose depth of insertion regulates the capacity of said cell and closed at its other end bya diaphragm of thin sheetrubber or equivalent substance, a heat-concentrating section of an electric circuit compressed into small bulk inclosed in said cell and extending therefrom by suitable counecting-wires, a drop of mercury alsoinclosed therein upon and around said heat-concentrating section and capable of being heated and expanded thereby and of exerting pressure upon said rubber diaphragm, and a switch bar, lover, or spring resting upon said diaphragm and moving therewith, substantially as described.

In testimony whereof I have signed my name to this specification, in the presence of two subscribing witnesses, this 2d day of March, 1892.

HARRY A. RHODES.

Witnesses:

E. 13. FIELD, E. M. BURGESS. 

